The formation of calcium oxalate kidney stones is known to have a strong genetic influence. Dr. Holmes has analyzed Ca excretion in a group of 101 normal individuals consuming self-selected diets. He believes that the distribution of Ca excretion is consistent with three excretory classes; this is the pattern of inheritance in 8 families he has studied to date. Dr. Holmes is examining the Ca excretion of individuals on diets where nutrients affecting Ca excretion are controlled.